Piezoelectric ceramic composition and piezoelectric ceramic electronic component

ABSTRACT

A main component has a general formula of {(1−x)(K 1-a-b Na a Li b ) m (Nb 1-c-d Ta c Sb d )O 3−x (M1 0.5 Bi 0.5 ) n M2O 3 } (wherein M1 is Ca, Sr or Ba, M2 is Ti, Zr or Sn, 0.005≦x≦0.5, 0≦a≦0.9, 0≦b≦0.3, 0≦a+b≦0.9, 0≦c≦0.5, 0≦d≦0.1, 0.9≦m≦1.1, and 0.9≦n≦1.1). At least one specific element selected from the group consisting of In, Sc, Y, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb and Lu is contained at as in sample numbers 46 to 48, 0.1 to 10 mol in total per 100 mols of the main component (preferably, 1.5 to 10 mol). This provides a piezoelectric ceramic composition and a piezoelectric ceramic electronic component that can have a desired high piezoelectric d constant in a consistent and highly efficient manner in both a very low electric field and a high electric field.

This is a continuation of application Ser. No. 11/517,484, filed Sep. 8,2006, now U.S. Pat. No. 7,754,095; which is a continuation ofPCT/JP2006/306353, filed Mar. 28, 2006, both of which are incorporatedherein by reference.

TECHNICAL FIELD

The present invention relates to a piezoelectric ceramic composition anda piezoelectric ceramic electronic component, and more particularly, toa piezoelectric ceramic composition, which does not contain Pb (lead),and a piezoelectric ceramic electronic component that includes thepiezoelectric ceramic composition, such as a piezoelectric actuator or apiezoelectric buzzer.

BACKGROUND ART

In recent years, considering reducing the load on the environment, alead-free piezoelectric ceramic composition has attracted attention. Ingeneral, lead-free piezoelectric ceramic composition is known to have alower piezoelectric d constant than a lead-based piezoelectric ceramiccomposition, such as PbTiO₃—PbZrO₃ (PZT).

Under such circumstances, a (K, Na)NbO₃-based piezoelectric ceramiccomposition, which has a relatively large piezoelectric d constant(piezoelectric distortion constant) among non-lead piezoelectric ceramiccompositions, has been studied actively.

For example, Patent Document 1 discloses a piezoelectric ceramiccomposition containing a main component having a general formula of(1−n)(K_(1-x-y)Na_(x)Li_(y))_(m)(Nb_(1-z)Ta_(z))O₃-nM1M2O₃ (wherein M1is a bivalent metallic element, and M2 is a quadravalent metallicelement). Patent Document 2 discloses a piezoelectric ceramiccomposition containing a main component having a general formula of(1−n)(K_(1-x-y)Na_(x)Li_(y))_(m)(Nb_(1-z)Ta_(z))O₃-nM1M2M3O₃ (wherein M1is a trivalent metallic element, M2 is a monovalent metallic element,and M3 is a tetravalent metallic element). In Patent Documents 1 and 2,x, y, z, m, and n are in the ranges of 0.1≦x, y≦0.3, x+y<0.75, 0≦z≦0.3,0.98≦m≦1.0, and 0<n<0.1.

In Patent Documents 1 and 2, a predetermined mol of a complex oxideM1M2O₃ or M1M2M3O₃ (for example, BaTiO₃, CaTiO₃, or(Na_(0.5)Bi_(0.5))TiO₃) of a perovskite type is dissolved as a componentin (K, Na, Li)(Nb, Ta)O₃. The resulting piezoelectric ceramiccomposition has a relative dielectric constant ∈r (=∈^(T)/∈₀; ∈^(T) isthe absolute dielectric constant, and ∈₀ is the dielectric constant offree space) of at least 1000, an electromechanical coupling factor kp ofat least 25%, and a Curie point Tc of more than 200 degrees C.

Patent Document 3 discloses a piezoelectric ceramic compositioncontaining 0.005 to 0.15 mol of at least one metallic element selectedfrom the group consisting of Ag, Al, Au, B, Ba, Bi, Ca, Ce, Co, Cs, Cu,Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Ho, In, Ir, La, Lu, Mg, Mn, Nd, Ni, Pd,Pr, Pt, Rb, Re, Ru, Sc, Si, Sm, Sn, Sr, Tb, Ti, Tm, V, Y, Yb, Zn and Zrper one mol of a main component having a general formula of{Li_(x)(K_(1-y)Na_(y))_(1-x)}(Nb_(1-z-w)Ta_(z)Sb_(w))O₃ (wherein0≦x≦0.2, 0≦y≦1, 0<z≦0.4, and 0<w≦0.2) and has a percentage of open poresof 0.4% by volume or less.

Patent Document 3 indicates that the addition of the at least onemetallic element selected from Ag to Zr described above to reduce thepercentage of open pores (the volume percentage of hollows in thesurface of a piezoelectric ceramic composition) to 0.4% by volume orless can improve the mechanical strength. In addition, Patent Document 3indicates that since the piezoelectric ceramic composition contains acomponent having the general formula of{Li_(x)(K_(1-y)Na_(y))_(1-x)}(Nb_(1-z-w)Ta_(z)Sb_(w))O₃ as a maincomponent, the piezoelectric ceramic composition can utilize a highpiezoelectric d constant and a high electromechanical coupling factor kpof the compound having the general formula to have these excellentcharacteristics.

Patent Document 4 discloses a piezoelectric ceramic composition having ageneral formula of {(K_(1-x)Na_(x))_(1-y)Ag_(y)}NbO_(3-z)[M^(α) ⁺][O²⁻]_(α) _(/2) (wherein 0≦x<1, 0≦y≦0.1, 0≦z≦0.05, and 0<y+z; M denotesat least one metallic element selected from the group consisting of Mn,Mg, In, Si, Ga, and Sb), and a is the average valence of a metallicelement M).

According to Patent Document 4, the addition of predetermined amounts ofAg and at least one metallic element selected from the group consistingof Mn, Mg, In, Si, Ga, and Sb to (K, Na)NbO₃ can decrease the dielectricloss tan δ, improve the reliability, and increase the piezoelectric dconstant.

[Patent Document 1 ] Japanese Unexamined Patent Application PublicationNo. 11-228227

[Patent Document 2 ] Japanese Unexamined Patent Application PublicationNo. 11-228228

[Patent Document 3 ] Japanese Unexamined Patent Application PublicationNo. 2004-244300

[Patent Document 4 ] Japanese Unexamined Patent Application PublicationNo. 2002-68835

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

While in Patent Documents 1 and 2 the addition of M1M2O₃ or M1M2M3O₃ to(K, Na, Li)(Nb, Ta)O₃ as a third component provides a relativedielectric constant ∈r as high as at least 1000, the increase in thecontent of the third component causes a decrease in theelectromechanical coupling factor kp. Thus, the piezoelectric d constantincreases slightly but insufficiently.

More specifically, the relationship among the piezoelectric d constant,the dielectric constant ∈^(T), and the electrical coupling factor kp isexpressed by a numerical formula (1):

$\begin{matrix}{d = {{kp}\sqrt{\frac{ɛ^{T}}{Y}}}} & (1)\end{matrix}$wherein Y denotes Young's modulus.

Thus, it is desirable that both the relative dielectric constant ∈r andthe electromechanical coupling factor kp are increased to yield a highpiezoelectric d constant. However, although only the addition of M1M2O₃or M3M4M2O₃ as a third component to (K, Na, Li)(Nb, Ta)O₃ as in PatentDocuments 1 and 2, may increase the relative dielectric constant ∈r, theincrease in the content of the third component causes a decrease in theelectromechanical coupling factor kp. Thus, there is a problem that adesired sufficiently high piezoelectric d constant cannot be obtained.

Patent Document 3 describes that the addition of a metallic element,such as In, to {Li_(x)(K_(1-y)Na_(y))_(1-x)}(Nb_(1-z-w)Ta_(z)Sb_(w))O₃can reduce the percentage of open pores to 0.4% by volume or less.According to an experiment by the present inventors, it was found thatthe piezoelectric d constant was not increased remarkably, and apiezoelectric ceramic composition having a desired high piezoelectric dconstant could not be obtained.

Patent Document 4 describes that the addition of Ag and, for example, Into (K, Na)NbO₃ increases d₃₁. However, it was found that the increasewas small and a piezoelectric ceramic composition having a sufficientlyhigh piezoelectric d constant could not be obtained.

Furthermore, with the recent technical progress in the preparation ofthinner ceramics, a high-field driven stacked piezoelectric ceramicelectronic component has been developed and put to practical use.

It is desired that a piezoelectric material for a high electric fielddriven piezoelectric ceramic electronic component have a highpiezoelectric d constant in the high electric field practically used.However, the piezoelectric d constant in a high electric fieldpractically used is generally different from the piezoelectric dconstant usually measured in a very low electric field. Thus, a highpiezoelectric d constant in a very low electric field does not alwaysmean there is a high piezoelectric d constant in a high electric field.

More specifically, a piezoelectric material includes a large number ofregions exhibiting spontaneous polarization in different directions,called domains. In a very low electric field, the only responsive domainis 180° domains exhibiting spontaneous polarization parallel to thedirection of the electric field applied. In a high electric field, inaddition to the response of the 180° domains, 90° domains, which exhibitspontaneous polarization perpendicular to the direction of the electricfield applied, turn toward the direction of the electric field applied,generating a large distortion. Thus, the piezoelectric d constant in ahigh electric field can be greater than that in a very low electricfield. However, in a high electric field having a strength beyond acertain electric field strength where most of the 90° domains become180° domains, a large displacement can no longer be achieved. Thestructure of a domain may vary with the composition of a piezoelectricmaterial. Thus, even when a piezoelectric material has a highpiezoelectric d constant in a very low electric field, the piezoelectricmaterial may not have a high piezoelectric d constant in a high electricfield in a manner that depends on the domain structure.

Studies by the present inventors showed that in known lead-freepiezoelectric ceramic compositions as described in Patent Documents 1 to4, the piezoelectric d constant in a very low electric field may beincreased slightly but insufficiently, and the piezoelectric d constantin a high electric field is much smaller than the desired piezoelectricd constant.

The present invention was accomplished in light of such circumstances.Accordingly, it is an object of the present invention to provide anon-lead piezoelectric ceramic composition that can achieve desired highpiezoelectric d constants in both a very low electric field and a highelectric field and a piezoelectric ceramic electronic component producedusing the piezoelectric ceramic composition.

Means for Solving the Problems

To achieve the object described above, the present inventors haveconducted an intense study and found that a piezoelectric ceramiccomposition that contains a main component prepared by dissolvingM1_(0.5)Bi_(0.5)M2O₃ (wherein M1 is K or Na, and M2 is Ti, Zr or Sn)having a perovskite structure as a component in a (K, Na, Li)(Nb, Ta,Sb)O₃-based compound having a predetermined molar ratio and anotherperovskite structure, and also contains about 0.1 to 10 mol in total ofat least one specific element selected from the group consisting of In,Sc, Y, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb and Lu per 100 mol of the maincomponent can have an increased relative dielectric constant ∈r, anincreased electromechanical coupling factor kp, a high Curie point Tc,and the desired high piezoelectric d constants in both a very lowelectric field and a high electric field.

The present invention was achieved on the basis of such findings. Apiezoelectric ceramic composition according to the present inventioncontains a main component having a general formula of{(1−x)(K_(1-a-b)Na_(a)Li_(b))_(m)(Nb_(1-c-d)Ta_(c)Sb_(d))O₃-x(M1_(0.5)Bi_(0.5))_(n)M2O₃}(wherein M1 is at least one metallic element selected from the groupconsisting of K and Na, M2 is at least one metallic element selectedfrom the group consisting of Ti, Zr and Sn, and x, a, b, c, d, m and nare in the ranges of 0.005≦x≦0.5, 0≦a≦0.9, 0≦b≦0.3, 0≦a+b≦0.9, 0≦c≦0.5,0≦d≦0.1, 0.9≦m≦1.1, and 0.9≦n≦1.1, respectively), and about 0.1 to 10mol in total of at least one specific element selected from the groupconsisting of In, Sc, Y, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb and Lu per100 mols of the main component.

It was also found that when the piezoelectric ceramic composition isprepared to have the molar ratio m of (K_(1-a-b)Na_(a)Li_(b)) and(Nb_(1-c-d)Ta_(c)Sb_(d)) in the range of 0.9≦m≦0.99, the piezoelectric dconstant in a high electric field can be improved further efficiently.

Thus, the m is preferably in the range of 0.9≦m≦0.99 in a piezoelectricceramic composition according to the present invention.

A known piezoelectric ceramic composition containing (K, Na)NbO₃ as amain component has a very narrow firing temperature range for preparinga satisfactory sintered compact. Practically, this causes a seriousproblem in mass production. Thus, it is desired that a satisfactorysintered compact can be prepared in a wider firing temperature range.

The present inventors have conducted an intense study and found thatwhen a piezoelectric ceramic composition is prepared to contain about1.5 to 10 mol in total of the specific element described above per 100mol of the main component, the temperature range ΔT under which stablefiring can be performed can be increased. Thus, fluctuations in thefiring temperature during sintering have a smaller effect. This canreduce the number of defectives and thus increase productivity.

Thus, a piezoelectric ceramic composition according to the presentinvention preferably contains about 1.5 to 10 mol in total of thespecific element per 100 mols of the main component.

In addition, it was found that the presence of about 0.1 to 10 mol intotal of at least one metallic element selected from the groupconsisting of Mn, Ni, Fe, Zn, Cu and Mg per 100 mols of the maincomponent can further increase the firing temperature range ΔT.

Thus, the piezoelectric ceramic composition according to the presentinvention may further contain about 0.1 to 10 mol in total of at leastone metallic element selected from the group consisting of Mn, Ni, Fe,Zn, Cu and Mg per 100 mols of the main component.

A piezoelectric ceramic electronic component according to the presentinvention includes an external electrode disposed on a surface of apiezoelectric ceramic element, wherein the piezoelectric ceramic elementis formed of the piezoelectric ceramic composition described above.

Furthermore, the piezoelectric ceramic element may include an internalelectrode in the piezoelectric ceramic electronic component according tothe present invention.

Advantages of the Invention

A piezoelectric ceramic composition according to the present inventioncontains a main component having a general formula of{(1−x)(K_(1-a-b)Na_(a)Li_(b))_(m)(Nb_(1-c-d)Ta_(c)Sb_(d))O_(3-X)(M1_(0.5)Bi_(0.5))_(n)M2O₃}(wherein M1 is at least one metallic element selected from the groupconsisting of K and Na, M2 is at least one metallic element selectedfrom the group consisting of Ti, Zr and Sn, and x, a, b, c, d, m and nare in the ranges of 0.005≦x≦0.5, 0≦a≦0.9, 0≦b≦0.3, 0≦a+b≦0.9, 0≦c≦0.5,0≦d≦0.1, 0.9≦m≦1.1, and 0.9≦n≦1.1, respectively, and about 0.1 to 10 molin total of at least one specific element selected from the groupconsisting of In, Sc, Y, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb and Lu per100 mols of the main component. Thus, the piezoelectric d constant canbe increased in both a very low electric field and a high electricfield. Specifically, a piezoelectric ceramic composition thus producedcan have excellent piezoelectric characteristics: the piezoelectric d₃₃constant in a very low electric field is at least 105 pC/N and thepiezoelectric d constant in a high electric field is at least 150 pC/N.

Furthermore, a piezoelectric ceramic composition according to thepresent invention can have further improved piezoelectriccharacteristics when the m is in the range of 0.9≦m≦0.99. Specifically,a piezoelectric ceramic composition thus produced can have apiezoelectric d₃₃ constant in a very low electric field of at least 110pC/N and the piezoelectric d constant in a high electric field of atleast 180 pC/N.

Preferably, a piezoelectric ceramic composition according to the presentinvention contains about 1.5 to 10 mol in total of the specific elementper 100 mol of the main component. This can increase the temperaturerange ΔT for stable firing and reduce the number of defectives even inthe presence of fluctuations in the firing temperature. Specifically,the temperature range ΔT can be at least about 20 degrees C. Thus, theproductivity can be improved.

Preferably, a piezoelectric ceramic composition according to the presentinvention further contains about 0.1 to 10 mol in total of at least onemetallic element selected from the group consisting of Mn, Ni, Fe, Zn,Cu and Mg per 100 mols of the main component. This can further increasethe firing temperature range ΔT. Specifically, the addition of thebivalent metallic element described above can further increase thefiring temperature range ΔT by about 10 to about 25 degrees C. Thus, thetemperature range ΔT can be increased by about 45 to about 60 degrees C.in total.

A piezoelectric ceramic electronic component according to the presentinvention includes an external electrode disposed on a surface of apiezoelectric ceramic element, wherein the piezoelectric ceramic elementis formed of the piezoelectric ceramic composition described above.Thus, a piezoelectric ceramic electronic component having a highpiezoelectric constant in not only a very low electric field but also ahigh electric field can consistently be produced.

A piezoelectric ceramic electronic component according to the presentinvention may have a piezoelectric ceramic element including an internalelectrode. Thus, even a high-field driven stacked piezoelectric ceramicelectronic component, such as a piezoelectric actuator, can have a highpiezoelectric d constant at a driving electric field. Thus, apiezoelectric ceramic electronic component having excellentpiezoelectric characteristics can be produced in a consistent and highlyefficient manner.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic single view drawing of a perovskite oxygenoctahedral structure.

FIG. 2 is a cross-sectional view of a stacked piezoelectric actuator asa piezoelectric ceramic electronic component according to one embodimentof the present invention.

REFERENCE NUMERALS

1 piezoelectric ceramic element

2 a, 2 b external electrode

3 internal electrode

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be further illustrated with embodimentsbelow.

A piezoelectric ceramic composition according to one embodiment (firstembodiment) of the present invention is expressed by a general formula(A):100{(1-x)(K_(1-a-b)Na_(a)Li_(b))_(m)(Nb_(1-c-d)Ta_(c)Sb_(d))O_(3-X)(M1_(0.5)Bi_(0.5))_(n)M2O₃}+(α/2)X₂O₃   (A)

wherein M1 is at least one metallic element selected from the groupconsisting of K and Na, M2 is at least one metallic element selectedfrom the group consisting of Ti, Zr and Sn, and X is at least onespecific element selected from the group consisting of In, Sc, Y, Nd,Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb and Lu.

The α, x, a, b, c, d, m and n satisfy numerical formulas (2) to (10):0.1≦α≦10   (2)0.005≦x≦0.5   (3)0≦a≦0.9   (4)0≦b≦0.3   (5)0≦a+b≦0.9   (6)0≦c≦0.5   (7)0≦d≦0.1   (8)0.9≦m≦1.1   (9)0.9≦n≦1.1   (10)

Thus, the piezoelectric ceramic composition contains a main component{(K_(1-a-b)Na_(a)Li_(b))_(m)(Nb_(1-c-d)Ta_(c)Sb_(d))O₃-(M1_(0.5)Bi_(0.5))_(n)M2O₃}of a perovskite structure (general formula ABO₃) prepared to have apredetermined molar ratio and about 0.1 to 10 mol of a specific elementX, such as In or Sc, per 100 mols of the main component. Thepiezoelectric ceramic composition can have high piezoelectric dconstants in both a very low electric field and a high electric fieldand desired piezoelectric characteristics.

In other words, as described in Background Art, a solid solution of aperovskite complex oxide component having a specific compositiondissolved as a third component in (K, Na, Li)(Nb, Ta)O₃ can have a highpiezoelectric d constant. However, a simple solid solution of aperovskite complex oxide component having a specific composition onlydissolved in (K, Na, Li)(Nb, Ta)O₃ cannot have a sufficiently highpiezoelectric d constant (for example, at least 100 pC/N). The simplesolid solution has piezoelectric characteristics inferior to those of alead-based piezoelectric ceramic composition particularly in a highelectric field.

As illustrated in FIG. 1, a perovskite structure has a B siteion-centered oxygen octahedral skeleton and an A site ion coordinatingin the skeletal space. In FIG. 1, P represents an oxygen octahedralskeleton, a black sphere represents a B site ion, a hatched sphererepresents an A site ion, and a white sphere represents an O²⁻ ion.

In (K, Na)NbO₃, for example, the A site ions K⁺and Na⁺coordinate in a Bsite ion Nb⁵⁺-centered oxygen octahedral skeleton. In(Na_(0.5)Bi_(0.5))_(n)TiO₃, A site ions Na⁺and Bi³⁺coordinate in a Bsite ion Ti⁴⁺-centered oxygen octahedral skeleton.

To prepare a uniform solid solution of complex oxides of differentcompositions having the perovskite structure, their B site ion-centeredoxygen octahedral structures must naturally be commensurate with eachother.

When the valencies of B site ions are identical as in (K, Na)NbO₃ andLiSbO₃, the B site ions Nb⁵⁺ and Sb⁵⁺blend with each other relativelyfreely. Thus, a totally uniform oxygen octahedral skeleton can be formedin a solid solution of these, and their B site ion-centered oxygenoctahedral structures can be commensurate with each other.

However, when a solid solution is prepared from perovskite complexoxides having different B site ion valencies, such as (K, Na)NbO₃ and(Na_(0.5)Bi_(0.5))_(n)TiO₃, only Nb⁵⁺ ions dissolve in the surroundingsof a K⁺ ion and only Ti⁴⁺ ions dissolve in the surroundings of a Bi³⁺ion to maintain the balance of local charges. Thus, the Nb⁵⁺ ions andthe Ti⁴⁺ ions cannot blend with each other freely and form oxygenoctahedral structures having different sizes. In this case, the oxygenoctahedral structures between the perovskite complex oxides commensuratepoorly with each other. This makes it difficult to prepare an excellentpiezoelectric ceramic composition, compromising the piezoelectricity.

In the present embodiment, the addition of a predetermined mol of aspecific element, such as In or Sc, to the main component allows oxygenoctahedral structures of different perovskite complex oxides to becommensurate with each other, providing high piezoelectric d constantsin both a very low electric field and a high electric field.

More specifically, when In, for example, in an oxide form is added as aspecific element in addition to (K_(0.5)Na_(0.5))NbO₃ and(Na_(0.5)Bi_(0.5))_(n)TiO₃, as shown in reaction formula (B), part of Inreplaces part of K and Na in (K_(0.5)Na_(0.5))NbO₃ and part of Ti in(Na_(0.5)Bi_(0.5))_(n)TiO₃. Furthermore, In acts to maintain the totalbalance of charges and blends with part of Nb and Ti.100{(1−x)(K_(0.5)Na_(0.5))NbO₃+x(Na_(0.5)Bi_(0.5))_(n)TiO₃}+(α/2)In₂O₃→100{(1−x−(α/200))(K_(0.5)Na_(0.5))NbO₃−(x−α/100))(Na_(0.5)Bi_(0.5))_(n)TiO₃−(α/100)(K_(0.25)Na_(0.25)In_(0.5))TiO₃−(α/100)(Na_(0.5)Bi_(0.5))(In_(0.5)Nb_(0.5))O₃}  (B)

Since In³⁺ ions blend with A site ions and B site ions, the mixed layerreduces mismatching between different perovskite complex oxides to benaturally commensurate with each other, thus forming a matching layer.The presence of a matched layer of{(α/100)(K_(0.25)Na_(0.25)In_(0.5))TiO₃−(α/100)(Na_(0.5)Bi_(0.5))(In_(0.5))O₃}can provide a sufficiently high piezoelectric d constant even in a verylow electric field. Since the matching layer is believed to form adomain wall, a large number of small domains are expected to be formed,as compared with a solid solution of perovskite complex oxides havingthe same valency of B site ions. Each of the large number of smalldomains expand, contract, and rotate in a high electric field togenerate large deformation and distortion in total. This achieves a muchhigher piezoelectric d constant in a high electric field than that of asolid solution of perovskites having the same valency of B site ions.This may provide a piezoelectric ceramic composition having excellentpiezoelectric characteristics and a high piezoelectric d constant in notonly a very low electric field but also a high electric field.

The specific element X is limited to at least one element selected fromthe group consisting of In, Sc, Y, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yband Lu. Although all the specific elements X described above aretrivalent metallic elements, it does not mean that any trivalentmetallic element can be used. For example, Bi or La is not appropriateas an additive element. Thus, the specific element X is limited to themetallic elements described above.

Then, reasons that α, x, a, b, c, d, m and n are limited to the rangesof the numerical formulas (2) to (10) are described in detail below.

(1) α

The addition of a specific element, such as In, can increase thepiezoelectric d constants in both a very low electric field and a highelectric field. To this end, the number of moles a of the specificelement X should be at least about 0.1 mol per 100 mols of the maincomponent. However, when the number of moles a of the specific element Xis more than about 10 mol per 100 mols of the main component, thecontent of the specific element X exceeds the solubility limit. Thespecific element X that cannot be dissolved in a solid solution may beprecipitated on the grain boundary to form a conductive layer, causingpoor polarization.

Thus, a piezoelectric ceramic composition is prepared to have the numberof moles α of the specific element X per 100 mol of the main componentin the range of in the present embodiment, 0.1≦α≦10 in the presentembodiment.

When the number of moles a is in the range of 1.5≦α≦10, the temperaturerange ΔT for stable firing can be increased.

In a known piezoelectric ceramic composition, the temperature range ΔTfor stable firing is very narrow. Fluctuations in the firing temperaturemay increase the occurrence of defectives and decrease the productivity.

The present inventors found that the number of moles α of the specificelement X in the range of 1.5≦α≦10 per 100 mol of a main componentallows the temperature range ΔT for stable firing to be increased. Thisallows a margin for fluctuations in the firing temperature; a littlefluctuation in the firing temperature is not detrimental to sintering.Thus, a piezoelectric ceramic composition having excellent piezoelectriccharacteristics can be produced in a consistent and highly efficientmanner. Specifically, the firing temperature range ΔT can be at least 20degrees C. Thus, the number of moles a of the specific element X ispreferably in the range of 1.5≦α≦10 per 100 mol of the main component.

(2) x

x defines the molar ratio of a third component(M1_(0.5)Bi_(0.5))_(n)M2O₃ in a main component. When x is less than0.005, the content of (M1_(0.5)Bi_(0.5))_(n)M2O₃ is too low. Thisdecreases the relative dielectric constant ∈r and the electromechanicalcoupling factor kp. Thus, a desired high piezoelectric d constant cannotbe achieved, and the piezoelectric characteristics cannot be improved.When x is more than 0.5, the Curie point Tc decreases remarkably and theelectromechanical coupling factor kp decreases rapidly and thepiezoelectric characteristics become deteriorated.

Thus, components of a composition in the present embodiment are preparedso that x is in the range of 0.005≦x≦0.5.

(3) a, b

Na and Li are contained in a main component if necessary. Na and Lireplace part of K in a solid solution. When a, which defines the molarratio of Na, exceeds 0.9, a ferroelectric cannot be formed. When b,which defines the molar ratio of Li, exceeds 0.3, the amount of Liexceeds the solubility limit with K. Both cases result in lack ofpiezoelectricity. Furthermore, when the total of a and b exceeds 0.9,the relative dielectric constant ∈r decreases remarkably. Thus, adesired high piezoelectric d constant cannot be achieved.

Thus, components of a composition in the present embodiment are preparedso that a and b are in the ranges of 0≦a≦0.9, 0≦b≦0.3, and 0≦a+b≦0.9.

(4) c

Ta is also contained in a main component if necessary. Ta replaces partof Nb in a solid solution. When c, which defines the molar ratio of Ta,exceeds 0.5, the electromechanical coupling factor kp decreases greatly,the piezoelectric d constants in both a very low electric field and ahigh electric field decrease remarkably, and thus desired piezoelectriccharacteristics cannot be obtained.

Thus, components of a composition in the present embodiment are preparedso that c is in the range of 0≦c≦0.5.

(5) d

Sb is contained in a main component if necessary. Sb replace part of Nbin a solid solution. When d, which defines the molar ratio of Sb,exceeds 0.1, the Curie point Tc decreases remarkably. This results inlack of piezoelectricity.

Thus, components of a composition in the present embodiment are preparedso that d is in the range of 0≦d≦0.1.

(6) m

m defines the molar ratio of A sites and B sites in(K_(1-a-b)Na_(a)Li_(b))_(m)(Nb_(1-c-d)Ta_(c)Sb_(d))O₃. When m is lessthan 0.9, the molar ratio of an A site is too small. This greatlydecreases the electromechanical coupling factor kp and remarkablydecreases the piezoelectric d constants in both a very low electricfield and a high electric field. Thus, desired piezoelectriccharacteristics cannot be obtained. When m exceeds 1.1, the molar ratioof an A site becomes excessive. This causes poor sintering.

Thus, components of a composition in the present embodiment are preparedso that m is in the range of 0.9≦m≦1.1. Preferably, m is in the range of0.9≦m≦0.99 to achieve a higher piezoelectric d constant.

(7) n

n defines the molar ratio of A sites and B sites in(M1_(0.5)Bi_(0.5))_(n)M2O₃. When n is less than 0.9 or more than 1.1,the electromechanical coupling factor kp decreases greatly, and thepiezoelectric d constants in both a very low electric field and a highelectric field decrease remarkably. Thus, desired piezoelectriccharacteristics cannot be obtained. When n exceeds 1.1, the molar ratioof an A site becomes excessive. This causes poor sintering.

Thus, components of a composition in the present embodiment are preparedso that n is in the range of 0.9≦n≦1.1.

In the present embodiment, a piezoelectric ceramic composition havingthe general formula (A) is prepared to satisfy the numerical formulas(2) to (10). This can provide a piezoelectric ceramic composition havinghigh piezoelectric d constants in both a very low electric field and ahigh electric field and excellent piezoelectric characteristics.

Furthermore, a piezoelectric ceramic composition is prepared so that thenumber of moles α of the specific element X is in the range of 1.5≦α≦10per 100 mol of a main component. Thus, the temperature range ΔT forstable firing can be increased. This allows a piezoelectric ceramiccomposition having a desired piezoelectric d constant and excellentpiezoelectric characteristics to be produced in a consistent and highlyefficient manner. Thus, the productivity can be improved.

The present invention is not limited to the piezoelectric ceramiccomposition according to the embodiment described above. It is alsopreferred to add in the present embodiment, 0.1 to 10 mol of at leastone element selected from the group consisting of Mn, Ni, Fe, Zn, Cu andMg to 100 mols of a main component composed of a solid solution in ageneral formula (A). This can further increase the firing temperaturerange ΔT and further improve the productivity (second embodiment).

In this case, a piezoelectric ceramic composition can be expressed by ageneral formula (C):100{(1−x−y)(K_(1-a-b)Na_(a)Li_(b))_(m)(Nb_(1-c-d)Ta_(c)Sb_(b))O_(3-X)(M1_(0.5)Bi_(0.5))_(n)M2O₃}(α/2)X₂O₃+β[Z^(q+)][O²⁻]_((q/2))   (C)wherein Z is at least one metallic element selected from the groupconsisting of Mn, Ni, Fe, Zn, Cu and Mg.

The reason that the addition of Mn, Ni, Fe, Zn, Cu or Mg to the maincomponent can increase the firing temperature range ΔT is thought to bethat the element dissolved in a crystal grain serves to compensate forthe charge and facilitates the formation of a matching layer and therebyimproves sintering.

The reason that the additive level is in the present embodiment, 0.1 to10 mol per 100 mols of the main component is that at least in thepresent embodiment, 0.1 mol per 100 mol of a main component is requiredto further increase the firing temperature range ΔT, and that theadditive level of more than in the present embodiment, 10 mol may causepoor sintering.

Thus, when Mn, Ni, Fe, Zn, Cu or Mg is added to a main component, thepreparation should be performed so that its content is in the presentembodiment, 0.1 to 10 mol per 100 mols of the main component.

A piezoelectric ceramic electronic component produced using thepiezoelectric ceramic composition described above is described below.

FIG. 2 is a cross-sectional view of a stacked piezoelectric actuator asa piezoelectric ceramic electronic component according to one embodimentof the present invention. The stacked piezoelectric actuator includes apiezoelectric ceramic element 1, external electrodes 2 (2 a and 2 b)formed on both ends of the piezoelectric ceramic element 1 and composedof an electrical conductivity material, such as Ag, and internalelectrodes 3 (3 a to 3 g) included in parallel with each other in theopposite direction in the piezoelectric ceramic element 1 and composedof an electrical conductive material, such as Ag or Ag—Pd.

In the stacked piezoelectric actuator, one end of each of the internalelectrodes 3 a, 3 c, 3 e, and 3 g is electrically connected to oneexternal electrode 2 a, and one end of each of the internal electrodes 3b, 3 d, and 3 f is electrically connected to the other externalelectrode 2 b. When a voltage is applied between the external electrode2 a and the external electrode 2 b, the stacked piezoelectric actuatorshifts in a stacked direction indicated by an arrow X because of alongitudinal piezoelectric effect.

A method for manufacturing the stacked piezoelectric actuator isdescribed in detail below.

Predetermined amounts of at least one compound selected from the groupconsisting of TiO₂, ZrO₂ and SnO₂; at least one compound selected fromthe group consisting of In₂O₃, Sc₂O₃, Y₂O₃, Nd₂O₃, Sm₂O₃, Eu₂O₃, Gd₂O₃,Tb₄O₇, Dy₂O₃, HO₂O₃, Er₂O₃, Yb₂O₃ and Lu₂O₃; K₂CO₃; Nb₂O₅; Bi₂O₃;Na₂CO₃, Li₂CO₃ if necessary; and at least one compound selected from thegroup consisting of MnCO₃, NiO, Fe₂O₃, ZnO, CuO and MgCO₃ if necessaryare weighed as raw materials for a ceramic. The weighed raw materialsare charged in a ball mill containing grinding media, such as zirconia,are wet-blended sufficiently, and are dried to yield a ceramic rawpowder.

Subsequently, the ceramic raw powder is calcined at a predeterminedtemperature (for example, 600 to 1000 degrees C.). The calcined powderis again wet-ground in a ball mill to produce a raw powder beforesintering.

Then, the raw powder before sintering and an organic binder arewet-blended to form a slurry. Subsequently, a ceramic green sheet isproduced, for example, by a doctor blade method.

Then, an electrical conductive paste containing a main component of Agor Ag—Pd for an internal electrode is used to screen-print the ceramicgreen sheet, thus forming an electrode pattern.

Then, the ceramic green sheets on which the electrode pattern isscreen-printed are stacked and are subsequently sandwiched betweenceramic green sheets on which no electrode pattern is screen-printed.These ceramic green sheets are attached by pressure to form a stackedbody. Then, the stacked body is cut into pieces having a predeterminedsize. The pieces are placed in an alumina case and are calcined at apredetermined temperature (for example, 250 to 500 degrees C.) to removethe binder. Then, the pieces are fired at a predetermined temperature(for example, 1050 to 1200 degrees C.) to form a piezoelectric ceramicelement including internal electrodes therein.

Subsequently, an electrical conductive paste, for example, containing Agfor an external electrode is applied to both ends of the piezoelectricceramic element, and is baked at a predetermined temperature (forexample, 750 to 850 degrees C.) to form external electrodes 2 a and 2 b.Then, prescribed poling is performed to produce a stacked piezoelectricactuator. It is essential only that the external electrodes 2 a and 2 bhave satisfactory adhesiveness. Thus, the external electrodes 2 a and 2b may be formed by a thin-film forming method, for example, sputteringor vacuum evaporation.

In the present embodiment, a stacked piezoelectric actuator is producedusing a piezoelectric ceramic composition according to the presentinvention. Even when a high electric field of 1 kV/mm is applied, thepiezoelectric actuator can have a large piezoelectric d constant andexhibit a large displacement.

The present invention is not limited to the embodiments described above.In those embodiments, a stacked piezoelectric actuator is described as apiezoelectric ceramic electronic component. The present invention canalso be applied to a single-plate piezoelectric actuator and a bimorphpiezoelectric actuator. Furthermore, it is needless to say that thepiezoelectric ceramic composition can be used in various piezoelectricceramic electronic components, such as a piezoelectric resonator, apiezoelectric buzzer, and a piezoelectric sensor.

Then, the present invention will be specifically described with Examplesbelow.

EXAMPLE 1

K₂CO₃, Na₂CO₃, Nb₂O₅, Bi₂O₃, TiO₂, ZrO₂, SnO₂, In₂O₃, Sc₂O₃, Yb₂O₃,Y₂O₃, Nd₂O₃, Eu₂O₃, Gd₂O₃, Dy₂O₃, Sm₂O₃, HO₂O₃, Er₂O₃, Tb₄O₇ and Lu₂O₃were prepared as raw materials for ceramics.

These raw materials for ceramics were weighed to prepare compositionsshown in Table 1. The weighed raw materials were wet-blended in alcoholin a ball mill for 18 hours. Each of the resulting mixtures was driedand calcined at 700 to 1000 degrees C.

Then, the calcined mixture was roughly ground. The ground mixture and aproper amount of an organic binder were wet-ground in a ball mill for 16hours and sifted through a 40-mesh sieve to control the particle size.

Then, the powder having a controlled particle size was pressed at apressure of 9.8×10⁷ to 1.96×10⁸ Pa into a discoidal compact having adiameter of 10 mm and a thickness of 1.2 mm. The compact was fired at atemperature of 1050 to 1200 degrees C. in the air for two hours toproduce a ceramic element.

A compact was fired for two hours every five degree C. between 1050 and1200 degrees C. The piezoelectric d₃₃ constant at each firingtemperature was measured with a d₃₃ meter. The firing temperature at amaximum piezoelectric d₃₃ constant was considered as an optimum firingtemperature. A firing temperature range in which at least 80% of themaximum piezoelectric d₃₃ constant can be achieved was considered as thefiring temperature range ΔT for stable firing.

Then, Ag electrodes were formed on both main surfaces of the ceramicelement by vacuum evaporation. Subsequently, the ceramic element waspolarized in an isolating oil at a bath temperature of 20 to 180 degreesC. by applying a 2 to 10 kV/mm direct-current voltage for 10 to 30minutes. Thus, compositions of sample numbers 1 to 27 having a generalformula of100{(1−x)(K_(0.5)Na_(0.5))_(0.98)NbO_(3-X)(M1_(0.5)Bi_(0.5))_(n)M2O₃}+(α/2)X₂O₃were prepared.

Table 1 illustrates the compositions of sample numbers 1 to 27.

TABLE 1 Composition: 100{(1 − x)(K_(0.5)Na_(0.5))_(0.98)NbO₃ − Samplex(M1_(0.5)Bi_(0.5))M2O₃} + (α/2)X₂O₃ No. x M1 M2 X α  1 0.05 Na Ti In 2 2 0.05 Na Ti Sc 2  3 0.05 Na Ti Yb 2  4 0.05 Na Ti Y 2  5 0.05 Na Ti Nd2  6 0.05 Na Ti Eu 2  7 0.05 Na Ti Gd 2  8 0.05 Na Ti Dy 2  9 0.05 Na TiSm 2 10 0.05 Na Ti Ho 2 11 0.05 Na Ti Er 2 12 0.05 Na Ti Tb 2 13 0.05 NaTi Lu 2 14 0.05 Na Ti Yb/In 1/1 15 0.05 Na Ti Y/In 1/1  16* 0.05 Na TiBi 2  17* 0.05 Na Ti La 2  18* 0.05 Na Ti — — 19 0.05 Na Ti In 0.1 200.05 Na Ti In 1 21 0.05 Na Ti In 1.5 22 0.05 Na Ti In 10  23* 0.05 Na TiIn 15 24 0.05 Na Zr In 2 25 0.05 Na Sn In 2 26 0.05 K Ti In 2 27 — — —In 2 *means outside of the scope of the present invention.

In the sample numbers 1 to 27, the relative dielectric constant ∈r, theelectromechanical coupling factor kp, the piezoelectric d₃₃ constant ina very low electric field (hereinafter referred to simply as“piezoelectric d₃₃ constant”), the piezoelectric d₃₃ constant measuredin a high electric field (hereinafter referred to as “piezoelectric d₃₃constant in a high electric field”), and the Curie point Tc weremeasured.

The relative dielectric constant ∈r was determined from the capacitancemeasured with an impedance analyzer and the sample size. Theelectromechanical coupling factor kp was determined by aresonance-antiresonance method using an impedance analyzer.

The piezoelectric d₃₃ constant was determined with a d₃₃ meter from theamount of electric charge generated under oscillation corresponding tothe application of an electric field of about 1 V/mm.

The piezoelectric d₃₃ constant in a high electric field was calculatedby measuring the displacement in the thickness direction in an electricfield of 1 kV/mm in the thickness direction with a displacement gage,calculating the distortion factor by dividing the displacement by thethickness, and dividing the distortion factor by the electric field.

The Curie point Tc was determined by analyzing a temperaturecharacteristic of the relative dielectric constant Er and calculatingthe temperature at a maximum relative dielectric constant ∈r.

Table 2 gives the measurements and the firing temperature ranges ΔT forsample numbers 1 to 27.

TABLE 2 Piezoelectric d₃₃ Relative Electromechanical Piezoelectric d₃₃constant in a high Firing temperature Sample dielectric coupling factorkp constant electric field Curie point Tc range ΔT No. constant εr (%)(pC/N) (pC/N) (° C.) (° C.)  1 790 50.1 242 393 310 35  2 765 47.3 221364 310 35  3 810 37.2 165 274 290 35  4 910 31.6 157 261 280 35  5 89027.0 130 218 290 25  6 896 29.4 143 239 290 25  7 810 29.2 133 223 30025  8 863 32.2 146 244 290 35  9 846 35.4 165 274 290 35 10 736 33.6 142237 300 35 11 856 35.2 165 274 290 35 12 860 27.2 121 210 290 35 13 76547.2 225 370 310 35 14 854 49.5 237 385 300 40 15 843 48.7 233 383 30040  16* 654 13.5 63 93 260 Low reproducibility  17* 573 11.8 52 74 270Fraction defective  18* 623 15.4 64 90 310 ≧95% 19 763 24.3 112 182 3105 20 772 24.8 114 186 310 10 21 788 48.3 231 381 310 30 22 782 49.5 230376 310 30  23* No piezoelectricity 24 675 46.3 201 332 310 40 25 57644.2 182 301 310 40 26 593 44.3 183 303 310 35 27 380 30.1 93 124 400 20*means outside of the scope of the present invention.

Sample numbers 1 to 17 contain a total of 2 mols of trivalent metallicelements per 100 mols of main component having a composition formula of{0.95 (K_(0.5)Na_(0.5))_(0.98)NbO₃-0.05(Na_(0.5)Bi_(0.5))TiO₃}.

Sample numbers 1 to 15 contain a specific element (In, Sc, Yb, Y, Nd,Eu, Gd, Dy, Sm, Ho, Er, Tb and Lu) according to the present invention.Thus, they have a high relative dielectric constant Er and a highelectromechanical coupling factor kp. As a result, sample numbers 1 to15 have piezoelectric d₃₃ constants of at least 105 pC/N andpiezoelectric d₃₃ constants in a high electric field of at least 150pC/N, and thus exhibit excellent piezoelectric characteristics.

Furthermore, it was found that when the number of moles α of eachmetallic element was 2 mol per 100 mol of a main component and was inthe range of 1.5 to 10 mol, the temperature range ΔT for stable firingcould be increased to 25 to 40 degrees C.

By contrast, sample numbers 16 and 17 contained Bi or La as a trivalentmetallic element (i.e., other than the specific element) and had verylow electromechanical coupling factors kp. Thus, sample numbers 16 and17 had low piezoelectric d33 constants and low piezoelectric d₃₃constants in a high electric field, and did not have the desiredpiezoelectric characteristics. Furthermore, the firing temperaturefluctuated. This resulted in poor reproducibility even when firing wasperformed at the same temperature. The fraction of defectives was atleast 95%. This is probably because Bi or La cannot dissolve in the Bsite of BaTiO₃, and a matched layer between (K_(0.5)Na_(0.5))NbO₃ and(Na_(0.5)Bi_(0.5))TiO₃ could not consistently be formed.

Sample number 18 did not contain an additive element in the maincomponent. As in sample numbers 16 and 17, sample number 18 had a verylow electromechanical coupling factor kp. As a result, sample number 18had a low piezoelectric d₃₃ constant and a low piezoelectric d₃₃constant in a high electric field, and did not have desiredpiezoelectric characteristics. Furthermore, the firing temperaturefluctuated. This resulted in poor reproducibility even when firing wasperformed at the same temperature. The fraction of defectives was atleast 95%.

These results showed that it is important to add the specific elementwithin the scope of the present invention to a main component to improvethe piezoelectric characteristics.

Sample numbers 19 to 23 contain different molar amounts of In for a maincomponent having a composition formula of{0.95(K_(0.5)Na_(0.5))_(0.98)NbO₃-0.05(Na_(0.5)Bi_(0.5))TiO₃}.

Sample number 23 was poorly polarized and did not exhibitpiezoelectricity. This is probably because the molar amount of In was amexcessive 15 mols per 100 mols of the main component, and In undissolvedin the main component was deposited on a grain boundary and formed aconductive layer.

By contrast, it was found that when 0.1 to 10 mol of In was added to 100mol of a main component, in sample numbers 19 to 22, that thepiezoelectric d₃₃ constants were at least 105 pC/N, the piezoelectricd₃₃ constants in a high electric field were at least 150 pC/N, and thusthe piezoelectric characteristics were excellent.

In sample numbers 21 and 22, the numbers of moles a of In were in samplenumbers 19 to 22, 1.5 to 10 mol per 100 mols of a main component, thepiezoelectric d₃₃ constants and the piezoelectric d₃₃ constants in ahigh electric field were further improved, as compared with samplenumbers 19 and 20. It was also found that the firing temperature rangesΔT were also increased. This is probably because when the In content wasless than 1.5 mol, a matching layer between (K_(0.5)Na_(0.5))NbO₃ and(Na_(0.5)Bi_(0.5))TiO₃ was insufficiently formed, the piezoelectriccharacteristics became slightly poorer, and the firing temperature rangeΔT was as narrow as 10 degrees C. or less, but when the In content wasat least 1.5 mol, a desired matching layer was formed and thereby adesired stable piezoelectric ceramic composition was prepared.

In sample numbers 24 to 26 containing different components of(M1_(0.5)Bi_(0.5))M2O₃ within the scope of the present invention, it wasfound that the piezoelectric d₃₃ constants were at least 105 pC/N, thepiezoelectric d₃₃ constants in a high electric field were at least 150pC/N, and thus the piezoelectric characteristics were excellent. It wasalso found that the firing temperature range ΔT could also be increasedto 35 to 40 degrees C. Thus, it was shown that at least one elementselected from the group consisting of Na and K could be used as M1, andat least one element selected from the group consisting of Ti, Zr and Sncould be used as M2.

In sample number 27, which did not contain (M1_(0.5)Bi_(0.5))M2O₃ in thecomposition, the piezoelectric d₃₃ constant was less than 105 pC/N and apiezoelectric d₃₃ constant in a high electric field was less than 150pC/N. Thus, it was shown that sample number 27 could not have desiredexcellent piezoelectric characteristics.

Embodiment 2

K₂CO₃, Na₂CO₃, Li₂CO₃, Nb₂O₅, Ta₂O₅, Sb₂O₅, Bi₂O₃, TiO₂ and In₂O₃ wereprepared as raw materials for ceramics. These raw materials for ceramicswere weighed to prepare the compositions shown in Table 3. Testspecimens of sample numbers 31 to 55 were produced by the same methodand procedures as in Example 1. The firing temperature range ΔT was alsodetermined as in Example 1.

The relative dielectric constant ∈r, the electromechanical couplingfactor kp, the piezoelectric d₃₃ constant, the piezoelectric d₃₃constant in a high electric field, and the Curie point Tc weredetermined by the method and procedures in Example 1.

Table 3 illustrates the compositions of sample numbers 31 to 55. Table 4illustrates the measurements and the firing temperature ranges ΔT forsample numbers 31 to 55.

TABLE 3 Composition: 100{(1 −x)(K_(1−a−b)Na_(a)Li_(b))_(m)(Nb_(1−c−d)Ta_(c)Sb_(d))O₃—x(Na_(0.5)Bi_(0.5))_(n)TiO₃} +Sample In₂O₃  No. x a b c d m n 31 0.005 0.5 0 0 0 0.98 1 32 0.1 0.5 0 00 0.98 1 33 0.3 0.5 0 0 0 0.98 1 34 0.5 0.5 0 0 0 0.98 1  35* 0.6 0.5 00 0 0.98 1 36 0.05 0 0 0 0 0.98 1 37 0.05 0.9 0 0 0 0.98 1  38* 0.050.95 0 0 0 0.98 1 39 0.05 0.35 0.3 0 0 0.98 1  40* 0.05 0.3 0.4 0 0 0.981 41 0.005 0.5 0 0.5 0 0.98 1  42* 0.005 0.5 0 0.6 0 0.98 1 43 0.005 0.50 0 0.1 0.98 1  44* 0.005 0.5 0 0 0.2 0.98 1  45* 0.05 0.5 0 0 0 0.80 146 0.05 0.5 0 0 0 0.90 1 47 0.05 0.5 0 0 0 0.95 1 48 0.05 0.5 0 0 0 0.991 49 0.05 0.5 0 0 0 1.00 1 50 0.05 0.5 0 0 0 1.10 1  51* 0.05 0.5 0 0 01.20 1  52* 0.005 0.5 0 0 0 0.98 0.8 53 0.005 0.5 0 0 0 0.98 0.9 540.005 0.5 0 0 0 0.98 1.1  55* 0.005 0.5 0 0 0 0.98 1.2 *means outside ofthe scope of the present invention.

TABLE 4 Piezoelectric d₃₃ Relative Electromechanical Piezoelectric d₃₃constant in a high Firing temperature Sample dielectric coupling factorkp constant electric field Curie point Tc range ΔT No. constant εr (%)(pC/N) (pC/N) (° C.) (° C.) 31 456 43.2 162 267 380 25 32 589 44.2 182296 350 30 33 1021 42.3 232 380 260 35 34 1523 32.3 212 345 150 35  35*No piezoelectricity 36 976 31.2 171 284 340 20 37 1056 27.6 153 255 31035  38* No piezoelectricity 39 778 41.2 192 314 310 35  40* Nopiezoelectricity 41 1643 33.4 225 368 130 35  42* 2120 5.9 53 70 50 3543 1420 38.4 243 390 180 35  44* No piezoelectricity  45* 678 10.8 53 60310 25 46 756 42.1 204 330 310 35 47 762 46.3 221 364 310 35 48 682 49.3223 366 310 35 49 583 28.4 109 153 310 35 50 563 27.8 105 150 310 35 51* — Poor sintering  52* 682 11.3 55 73 390 35 53 665 35.2 163 271 39035 54 693 34.3 154 256 390 35  55* 685 11.0 50 68 390 35 *means outsideof the scope of the present invention.

In sample number 35, x was 0.6, i.e., was more than 0.5, and the molaramount of a third component (Na_(0.5)Bi_(0.5))TiO₃ was excessive. Thus,sample number 35 was poorly polarized and did not exhibitpiezoelectricity. By contrast, it was shown that when x was in the rangeof 0.005 to 0.5, in sample numbers 31 to 34, a piezoelectric ceramicelectronic component having a piezoelectric d₃₃ constant of at least 105pC/N and a piezoelectric d₃₃ constant in a high electric field of atleast 150 pC/N and exhibiting excellent piezoelectric characteristicscould be produced.

In sample number 38, a was 0.95, i.e., was more than 0.9. Thus, themolar ratio of Na was excessive and exceeded the solubility limit withK. Thus, sample number 38 exhibited no piezoelectricity.

By contrast, it was shown in sample numbers 36 and 37 that when a was inthe range of 0 to 0.9, a piezoelectric ceramic electronic componenthaving a piezoelectric d₃₃ constant of at least 105 pC/N and apiezoelectric d₃₃ constant in a high electric field of at least 150 pC/Nand exhibiting excellent piezoelectric characteristics could beproduced.

In sample number 40, b was 0.4, that is was more than 0.3. The molarratio of Li was too large to form a ferroelectric phase. Thus, samplenumber 40 exhibited no piezoelectricity.

By contrast, it was shown in sample number 39 that when b was 0.3, apiezoelectric ceramic electronic component having a piezoelectric d₃₃constant of at least 105 pC/N and a piezoelectric d₃₃ constant in a highelectric field of at least 150 pC/N and exhibiting excellentpiezoelectric characteristics could be produced.

In sample number 42 where c was 0.6, i.e., was more than 0.5, thepiezoelectric d₃₃ constant was as low as 53 pC/N, the piezoelectric d₃₃constant in a high electric field was as low as 70 pC/N, and thus thepiezoelectric characteristics were poor.

By contrast, it was shown in sample number 41 that when c was 0.5, apiezoelectric ceramic electronic component having a piezoelectric d₃₃constant of at least 105 pC/N and a piezoelectric d₃₃ constant in a highelectric field of at least 150 pC/N and exhibiting excellentpiezoelectric characteristics could be produced.

In sample number 44, d was 0.2 and thus was more than 0.1. Thus, Sb wasexcessive and the Curie point Tc was decreased. Sample number 44 did notexhibit piezoelectricity.

By contrast, it was shown in sample number 43 that when d was 0.1, apiezoelectric ceramic electronic component having a piezoelectric d₃₃constant of at least 105 pC/N and a piezoelectric d₃₃ constant in a highelectric field of at least 150 pC/N and exhibiting excellentpiezoelectric characteristics could be produced.

In sample number 45, m was 0.80 and was thus less than 0.9, and thepiezoelectric d₃₃ constant was as low as 53 pC/N, the piezoelectric d₃₃constant in a high electric field was as low as 60 pC/N, and thus thepiezoelectric characteristics were poor.

In sample number 51, m was 1.20 and was therefore more than 1.1. Thiscaused poor sintering.

By contrast, m in sample numbers 46 to 50 was in the range of 0.9 to1.1. Thus, piezoelectric ceramic electronic components having apiezoelectric d₃₃ constant of at least 100 pC/N and a piezoelectric d₃₃constant in a high electric field of at least 200 pC/N and exhibitingexcellent piezoelectric characteristics could be produced.

In particular, it was found that when m was in the range of 0.9 to 0.99,as in sample numbers 46 to 48, the piezoelectric d₃₃ constants were atleast 200 pC/N, and the piezoelectric d₃₃ constants in a high electricfield were at least 330 pC/N, and thus the piezoelectric characteristicscould further be improved, as compared with sample numbers 49 and 50.

The reason for a slight degradation in the piezoelectric characteristicswhen m is more than 0.99 is probably that the amount of a component thatis to constitute an A site, such as K, increases, and thus an elementthat is not involved in the synthesis of a solid solution reactspreferentially with a tetravalent element constituting a B site of athird component, such as Ti, to form a secondary phase that partlyexhibits no piezoelectricity.

In sample number 52, it was found that when n was 0.8 and was thus lessthan 0.9, the piezoelectric d₃₃ constant was as low as 55 pC/N, thepiezoelectric d₃₃ constant in a high electric field was as low as 73pC/N, and thus the piezoelectric characteristics were poor.

In sample number 55, n was 1.2 and was therefore more than 1.1, and thepiezoelectric d₃₃ constant was as low as 50 pC/N, the piezoelectric d₃₃constant in a high electric field was as low as 68 pC/N, and thus thepiezoelectric characteristics were poor.

By contrast, n was in the range of 0.9 to 1.1 in sample numbers 53 and54. Thus, piezoelectric ceramic electronic components having apiezoelectric d₃₃ constant of at least 105 pC/N and a piezoelectric d₃₃constant in a high electric field of at least 150 pC/N and exhibitingexcellent piezoelectric characteristics could be produced.

These results showed that when the molar ratios of x, a, b, c, d, m andn in a main component are in the ranges of 0.005≦x≦0.5, 0≦a≦0.9,0≦b≦0.3, 0≦a+b≦0.9, 0≦c≦0.5, 0≦d≦0.1, 0.9≦m≦1.1, and 0.9≦n≦1.1, apiezoelectric ceramic electronic component having a piezoelectric d₃₃constant of at least 105 pC/N and a piezoelectric d₃₃ constant in a highelectric field of at least 150 pC/N and exhibiting excellentpiezoelectric characteristics can be produced.

Embodiment 3

A predetermined amount of Mn, Ni, Fe, Zn, Cu or Mg was added to thecomposition of sample number 1. Piezoelectric characteristics and thefiring temperature range ΔT were determined.

More specifically, K₂CO₃, Na₂CO₃, Nb₂O₅, Bi₂O₃, TiO₂, In₂O₃, MnCO₃, NiO,Fe₂O₃, ZnO, CuO and MgCO₃ were prepared as raw materials for ceramics.These raw materials for ceramics were weighed to prepare compositionsshown in Table 7. Test specimens of sample numbers 61 to 70 wereproduced by the same method and procedures as in Example 1. The firingtemperature range ΔT was also determined as in Example 1.

The relative dielectric constant ∈r, the electromechanical couplingfactor kp, the piezoelectric d₃₃ constant, the piezoelectric d₃₃constant in a high electric field, and the Curie point Tc weredetermined in sample numbers 61 to 70 by the method and procedures inExample 1.

Table 5 illustrates the compositions of sample numbers 61 to 70, variousmeasurements, and the firing temperature ranges ΔT, together with themeasurements and the firing temperature range ΔT in sample number 1.

TABLE 5100{0.95(K_(0.5)Na_(0.5))_(0.98)NbO₃—0.05(Na_(0.5)Bi_(0.5))TiO₃} +In₂O₃ + β[Z^(q+)][O²⁻]_((q/2)) Relative Piezoelectric d₃₃ dielectricElectromechanical coupling Piezoelectric d₃₃ constant in a high Firingtemperature Sample β constant εr factor kp constant electric field Curiepoint Tc range ΔT No. Z (mol) εr (%) (pC/N) (pC/N) (° C.) (° C.)  1 — 0790 50.1 242 393 310 35 61 Mn 1 612 38.2 166 265 310 55 62 Ni 1 644 40.8181 286 310 50 63 Fe 1 880 39.6 206 329 310 55 64 Zn 1 586 35.0 161 251310 60 65 Cu 1 589 36.3 163 248 310 60 66 Mg 1 850 37.5 191 298 310 5067 Mn 0.1 751 41.7 213 337 310 45 68 Mn 5 604 36.6 162 251 310 55 69 Mn10 505 32.3 126 190 310 50  70* Mn 15 — — — — — Poor sintering *meansoutside of the scope of the present invention (Claim 4).

As is evident from Table 5, 1 to 10 mol of Mn, Ni, Fe, Zn, Cu, or Mg wasadded to 100 mol of a main component in sample numbers 61 to 69.Compared with sample number 1, while the piezoelectric d₃₃ constants andthe piezoelectric d₃₃ constants in a high electric field were slightlydecreased, the piezoelectric d₃₃ constants were at least 105 pC/N, thepiezoelectric d₃₃ constants in a high electric field were at least 150pC/N, and the firing temperature ranges ΔT for stable sintering wereincreased to 45 to 60 degrees C. Thus, it was found that the firingtemperature ranges ΔT were wider by 10 to 25 degrees C. than samplenumber 1, and firing was possible in a wider temperature range ΔT.

In sample number 70, the molar amount of Mn was as large as 15 mol andwas thus more than 10 mols per 100 mols of the main component. Thiscaused poor sintering.

These results showed that the addition of as in sample numbers 46 to 48,1 to 10 mol of Mn, Ni, Fe, Zn, Cu or Mg per 100 mols of a main componentcan further increase the firing temperature range ΔT.

1. A piezoelectric ceramic composition comprising: a main componenthaving a general formula of{(1−x)(K_(1-a-b)Na_(a)Li_(b))_(m)(Nb_(1-c-d)Ta_(c)Sb_(d))O_(3-x)(M1_(0.5)Bi_(0.5))_(n)M2O₃}, wherein M1 is at least one metallic element selected from thegroup consisting of K and Na, M2 is at least one metallic elementselected from the group consisting of Ti, Zr and Sn, 0.005≦x≦0.5,0≦a≦0.9, 0≦b≦0.3, 0≦a+b≦0.9, 0≦c≦0.5, 0≦d≦0.1, 0.9≦m≦1.1, and 0.9≦n≦1.1;and at least one specific element selected from the group consisting ofIn, Sc, Y, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb and Lu per 100 mols in theform of an oxide in a total amount of about 0.1 to 10 mols per 100 molsof the main component.
 2. The piezoelectric ceramic compositionaccording to claim 1, wherein 0.9≦m≦0.99.
 3. The piezoelectric ceramiccomposition according to claim 2, wherein the specific element is about1.5 to 10 mol total per 100 mols of the main component.
 4. Thepiezoelectric ceramic composition according to claim 3, wherein M1comprises Na, M2 comprises Ti and the specific element comprises In. 5.The piezoelectric ceramic composition according to claim 4, wherein thecomposition further comprises Mn.
 6. A piezoelectric ceramic electroniccomponent comprising an external electrode disposed on a surface of apiezoelectric ceramic element, wherein the piezoelectric ceramic elementcomprises a piezoelectric ceramic composition according to claim
 5. 7.The piezoelectric ceramic electronic component according to claim 6,wherein the piezoelectric ceramic element includes an internalelectrode.
 8. The piezoelectric ceramic composition according to claim1, wherein the specific element is about 1.5 to 10 mols total per 100mols of the main component.
 9. A piezoelectric ceramic electroniccomponent comprising an external electrode disposed on a surface of apiezoelectric ceramic element, wherein the piezoelectric ceramic elementcomprises a piezoelectric ceramic composition according to claim
 8. 10.The piezoelectric ceramic electronic component according to claim 9,wherein the piezoelectric ceramic element includes an internalelectrode.
 11. A piezoelectric ceramic electronic component comprisingan external electrode disposed on a surface of a piezoelectric ceramicelement, wherein the piezoelectric ceramic element comprises apiezoelectric ceramic composition according to claim
 2. 12. Thepiezoelectric ceramic electronic component according to claim 11,wherein the piezoelectric ceramic element includes an internalelectrode.
 13. A piezoelectric ceramic electronic component comprisingan external electrode disposed on a surface of a piezoelectric ceramicelement, wherein the piezoelectric ceramic element comprises apiezoelectric ceramic composition according to claim
 1. 14. Thepiezoelectric ceramic electronic component according to claim 13,wherein the piezoelectric ceramic element includes an internalelectrode.
 15. The piezoelectric ceramic composition according to claim1, wherein M1 comprises Na, M2 comprises Ti and the specific elementcomprises In.
 16. A piezoelectric ceramic electronic componentcomprising an external electrode disposed on a surface of apiezoelectric ceramic element, wherein the piezoelectric ceramic elementcomprises a piezoelectric ceramic composition according to claim
 11. 17.The piezoelectric ceramic electronic component according to claim 16,wherein the piezoelectric ceramic element includes an internalelectrode.